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>Video for Linux Two API Specification: Revision 0.24</TH
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>ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN11616"
></A
><H2
>Name</H2
>VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT&nbsp;--&nbsp;Query or select the current video output</DIV
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CLASS="REFSYNOPSISDIV"
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><H2
>Synopsis</H2
><DIV
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><P
></P
><A
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></A
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int ioctl</CODE
>(int fd, int request, int *argp);</CODE
></P
><P
></P
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NAME="AEN11631"
></A
><H2
>Arguments</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><CODE
CLASS="PARAMETER"
>fd</CODE
></DT
><DD
><P
>File descriptor returned by <A
HREF="r14090.htm"
><CODE
CLASS="FUNCTION"
>open()</CODE
></A
>.</P
></DD
><DT
><CODE
CLASS="PARAMETER"
>request</CODE
></DT
><DD
><P
>VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT</P
></DD
><DT
><CODE
CLASS="PARAMETER"
>argp</CODE
></DT
><DD
><P
></P
></DD
></DL
></DIV
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><DIV
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><A
NAME="AEN11651"
></A
><H2
>Description</H2
><P
>To query the current video output applications call the
<CODE
CLASS="CONSTANT"
>VIDIOC_G_OUTPUT</CODE
> ioctl with a pointer to an integer
where the driver stores the number of the output, as in the
struct&nbsp;<A
HREF="r9149.htm#V4L2-OUTPUT"
>v4l2_output</A
> <CODE
CLASS="STRUCTFIELD"
>index</CODE
> field. This ioctl
will fail only when there are no video outputs, returning the
<SPAN
CLASS="ERRORCODE"
>EINVAL</SPAN
> error code.</P
><P
>To select a video output applications store the number of the
desired output in an integer and call the
<CODE
CLASS="CONSTANT"
>VIDIOC_S_OUTPUT</CODE
> ioctl with a pointer to this integer.
Side effects are possible. For example outputs may support different
video standards, so the driver may implicitly switch the current
standard. It is good practice to select an output before querying or
negotiating any other parameters.</P
><P
>Information about video outputs is available using the
<A
HREF="r9149.htm"
><CODE
CLASS="CONSTANT"
>VIDIOC_ENUMOUTPUT</CODE
></A
> ioctl.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN11663"
></A
><H2
>Return Value</H2
><P
>On success <SPAN
CLASS="RETURNVALUE"
>0</SPAN
> is returned, on error <SPAN
CLASS="RETURNVALUE"
>-1</SPAN
> and the <CODE
CLASS="VARNAME"
>errno</CODE
> variable is set appropriately:</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><SPAN
CLASS="ERRORCODE"
>EINVAL</SPAN
></DT
><DD
><P
>The number of the video output is out of bounds, or
there are no video outputs at all and this ioctl is not
supported.</P
></DD
><DT
><SPAN
CLASS="ERRORCODE"
>EBUSY</SPAN
></DT
><DD
><P
>I/O is in progress, the output cannot be
switched.</P
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